The US research, published in the American Journal of Infection Control, involved painting the nails of healthcare workers with standard polish and gel polish, with left some unpainted.
Researchers then measured bacterial contamination across 14 days.
They evaluated more than 700 bacterial cultures and found all nail types became contaminated over time regardless of the product applied, but gels were the worst.
Acrylic nails aren't recommend for healthcare workers but researchers say not as much is known about gel products.
All forms of gel require curing or hardening under an ultraviolet light and are popular because they are gentler on the natural nail and are supposed to stay intact for weeks. They can cost between $30 and $50.
Gel nails, or Shellac, have risen in popularity over recent years thanks to the likes of Kylie Jenner flashing them on social media.
In 2016 Vanessa Hudgens posted a photo of her decked out manicure for Coachella music festival, which, according to People, cost $US190 ($AU247) and took three hours to complete.
Hudgens, 27, went to Laqué Nail Bar in Hollywood where she spent almost three hours getting a brown coloured matte polish topped off with metallic images of pot leaves and real Swarovski crystals as decorations.
Over the years studies have revealed gel nail polish treatments can increase your risk of cancer because of the frequent exposure to UV light.
This study found all nail products tested become more contaminated with bacteria over time but standard polish and natural nails may be more amenable to hand hygiene than gel.
But researchers also highlighted the study did not show an increased number of microorganisms on nails with gel polish.
